A hammer drill is similar to a conventional drill/driver in that it uses rotational force to turn a drill bit or driver bit. However, it also uses a hammering function to create a vibrating action.
However, it also uses a hammering function to create a vibrating action, causing energy to be transferred to the chuck and the bit. The vibrating action causes the bit to chip away at whatever it’s hammering against. A hammer drill exerts force in line with the bit as it hits the material being drilled, making it the tool of choice for drilling holes in masonry and concrete. An impact driver is somewhat similar to a hammer drill, but it increases the force being delivered perpendicular to the bit, making it the preferred tool for driving large screws and lag bolts. A hammer drill shouldn’t be confused with a rotary hammer, which uses a piston, driven by a motor and gearing system, to pound a bit into material, which makes it a preferred tool among construction workers. In general, hammer drills are suitable both for drilling and driving long and wide screws and lag bolts into wood, and for hammer drilling holes up to about 3/4″ diameter in concrete block or brick. There are also hammer drill/driver tools that provide two modes of operation: a conventional “drilling and driving mode” that you use when accuracy in hole size and depth is crucial; and a “hammering mode” that adds a pounding force to the tool for extra-hard materials. Hammer drills are available in both corded and cordless formats.
Price: $70 to $400 (corded)
$100 – $550 (cordless with battery)
Cordless battery platform: 12V, 18/20V, 40V
Speed: up to 2,600 RPM
Pounding power: up to 39,000 BPM (blows per minute)
Torque: up to 1,250 in-lbs
Two hands required
Hammer drills are more powerful than drill/drivers. Almost all come with a 360° rotatable side handle – use it.
Use the right bit
Always use bits specifically rated for hammer drills. Carbide-tipped bits rated for percussion drilling are the best choice. If the tip of the bit gets damaged or becomes worn, replace it.
It’s often easier to start drilling with a smaller diameter drill bit and then switch to a larger bit to increase the hole to its final size.
Take it easy
Start on a low torque setting and increase it only if necessary. You only need to apply enough pressure to keep the hammer drill from bouncing or skipping around. Too much force slows down the tool and might cause it to overheat. Keep the drill perpendicular to the workpiece so that dust and debris can more easily exit the drill flutes.
Protect your eyes
Hammer drills throw out a lot of dust and chips. Always wear eye protection.